The present invention relates to solid-state displays and more specifically to edge-emitter reflective field emission pixel elements having shaped emitter elements for electron beam focusing for displays.
Solid state and non-Cathode Ray Tube (CRT) display technologies are well-known in the art. Light Emitting Diode (LED) displays, for example, include semiconductor diode elements that may be arranged in configurations to display alphanumeric characters. Alphanumeric characters are then displayed by applying a potential or voltage to specific elements within the configuration. Liquid Crystal Displays (LCD) are composed of a liquid crystal material sandwiched between two sheets of a polarizing material. When a voltage is applied to the sandwiched materials, the liquid crystal material aligns in a manner to pass or block light. Plasma displays conventionally use a neon/xenon gas mixture housed between sealed glass plates that have parallel electrodes deposited on the surface.
Passive matrix displays and active matrix displays are flat panel displays that are used extensively in laptop and notebook computers. In a passive matrix display, there is a matrix or grid of solid-state elements in which each element or pixel is selected by applying a potential to a corresponding row and column line that forms the matrix or grid. In an active matrix display, each pixel is further controlled by at least one transistor and a capacitor that is also selected by applying a potential to a corresponding row and column line. Active matrix displays provide better resolution than passive matrix displays, but they are considerably more expensive to produce.
While each of these display technologies has advantages, such as low power and lightweight, they also have characteristics that make them unsuitable for many other types of applications. Passive matrix displays have limited resolution, while active matrix displays are expensive to manufacture.
The edge emitter FED pixel element disclosed in U.S. patent application Ser. No. 10/102,450, entitled xe2x80x9cField-Emission Matrix Display Based on Electron Reflection,xe2x80x9d is representative of a pixel element that may be included in a low-cost, lightweight, high-resolution display system. In such a display, a high screen brightness with a minimum power consumption is advantageous. One method for achieving a high screen brightness is to concentrate the reflected electron beam onto an associated phosphor layer with little or no scattering, or cross-talk, of the electron beam from one pixel element into adjacent pixel elements, or as will be appreciated, an adjacent sub-pixel element.
Hence, there is a need for a method of concentrating or focusing the electron beam of edge-emitter FED pixel elements onto associated phosphor layers to substantially reduce electron beam cross-talk between adjacent elements.
An edge-emitter Field Emission Display (FED) pixel element and associated matrix display is disclosed. The FED pixel element has a reflector layer and an anode layer having a phosphor layer thereon, and a shaped emitter layer, which bounds a reflector layer and focuses a reflected electron beam to avoid scattering of the electron beam as it travels to the anode. Also disclosed is the use of high-voltage and high-voltage phosphor on the anode layer that advantageously improves the pixel element""s operational life. Also disclosed, is a method of determining the voltage on the anode layer to enhance the focusing of the electron beam based on the distance between the anode and the reflecting surface. In another aspect of the invention, a plurality of phosphor layers are applied to the transparent layer, which produce different levels of color as reflected electrons are attracted to the transparent layer and bombard corresponding phosphor layers.